The present invention relates generally to friction coatings. More particularly, the invention relates to a friction coating for a brake pad and a method of manufacture.
Various braking devices such as drum brake assembles and disc brake assemblies have been used in automobiles and other transport vehicles as a means to retard or stop vehicle motion. The assemblies typically have a pair of mutually opposed surfaces with a friction material thereon. In the case of disc brake assemblies, the rotor, which rotates along with the wheel and axle of the vehicle, is placed proximate a brake pad. The brake pad is movable axially relative to the rotor, the brake pad serving to retard or stop the motion of the rotor when in contact therewith. One problem with these assemblies is that the rotor can become scored or pitted to the point that replacement of the rotor is necessary. Another drawback commonly associated with these assemblies is the tendency to produce xe2x80x9csquealxe2x80x9d or undesirable low frequency vibrations or other noise caused by vibration during use, especially during the xe2x80x9cbreak in periodxe2x80x9d. Many different techniques have been used to create friction surfaces for the brake pads and/or rotors in order to overcome these drawbacks, with varying degrees of success.
In automotive brakes the rotor is normally gray iron, the rotor being bolted to the wheel which turns and the friction is caused by the caliper compressing the brake pad against the rotor. In automotive repair shops this brake rotor is normally turned or machined on a brake lathe prior to new brake pads being installed. The resulting surface of the rotor is not as smooth as the original surface when the rotor was new, and the surface may still retain many of the surfing imperfections. These surface imperfections contribute to squeal, vibration, brake dust, and excessive brake wear, thereby reducing the overall performance of the brake system.
U.S. Pat. No. 5,339,931 issued to Jacko et al. is directed to a friction material for a brake pad which includes copper powder. In accordance with the specification, scoring of the rotor is to be reduced by deforming and smearing of the copper powder as the brakes are applied. The copper powder, in response to temperatures generated by braking, produces a glaze covering the rotor which prevents scoring. The ""931 copper powder, which makes up from 2-18 percent by weight of the friction material, is distributed throughout the brake pad friction material at the time the brake pad is manufactured. The aluminum rotor is a relatively new technology designed for original equipment manufactures to be able to replace the current use of cast iron rotors with aluminum matrix rotors (AL-MMC). This is in an effort to reduce the overall weight of new vehicles to improve gas mileage. By contrast, the present invention is directed to a xe2x80x9cbreak inxe2x80x9d coating applied to conventional or any brake pads. Break in of the inventive pads, and reconditioning of the associated rotor, is simultaneously facilitated by the application of a coating containing a mixture of copper powder and resin to the friction surface of the brake pads. Application of the coated brake pads of the invention to the rotor during braking operations causes the mixture to be evenly spread upon the rotor surface, thereby causing the copper to fill any pores, cracks, and grooves which may be in the rotor during the break in period. It should be noted that the coated brake pads of the present invention are intended primarily for use with used rotors; as the new rotors already have a smooth friction surface. The mixture is applied after manufacture of the conventional brake pads and functions as an aftermarket performance enhancement for the brake system, the application process being adaptable for use at, e.g., an automobile repair facility.
In order to accomplish the objectives of the invention a vehicle brake assembly is provided with a brake friction pad coated in accordance with the inventive method to produce a protective layer upon an associated rotor or like element (e.g., brake shoe). The inventive coating is applied as a surface treatment to the friction material of the brake pad, application of the coating in accordance with the inventive method may be performed immediately after manufacture of the brake pad or as an aftermarket performance enhancement for the brake assembly. Copper powder suspended in a binder, such as resinous material, such as a phenolic resin, is the preferred material for the coating. Highly heat conductive materials of the relative consistency or softness of copper may substitute for copper. The process for coating the brake pad or rotor is adaptable for use at a repair facility or auto parts supply store in addition to being mass produced by a parts supplier, such as FCI Marketing, Inc. of St. Joseph, Mo., owned by the instant inventor. The protective layer is formed upon the rotor by pressure and heat generated during application of the brake pad to the rotor to retard or arrest rotation thereof. Grooves, pits, and other surface imperfections on the rotor surface are filled in by the protective layer, which is formed by transfer of the primarily copper powder of the coating, with just a few applications of the brake pad to the rotor. Noise, vibration, and excessive brake dust are all substantially reduced once the protective layer is formed.
Accordingly, it is a principal object of the invention to provide a new and improved coating for a brake pad.
It is a major object of the invention to provide a new and improved fiction coating for a brake pad which improves the performance of an adjacent rotor.
It is another object of the invention to provide a method of manufacturing a coated brake pad.
It is another object of the invention to provide a method for treating a rotor using a specially coated brake pad.
It is another object of the invention to provide a method of extending the life of a brake pad and rotor.
It is another object of the invention to provide a method of extending the life of a brake pad and an associated rotor by coating the brake pad so as to form a protective layer upon the rotor during the break-in period of a brake pad.
Finally, it is a general object of the invention to provide improved elements and arrangements thereof in an apparatus for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes.